National Geographic : 1927 Jul
THE NATIONAL GEOGRAPHIC MAGAZINE to resemble the leaves among which they live, striped to simulate the pine needles on which they feed or the grass on which they dwell, or colored to match the ground on which they crawl, many of them being unbelievably hard to see in their accus tomed surroundings. There are all kinds of moth and butter fly foes-birds that take the adult on the wing or in repose or eat the caterpillars; parasites that attack both the eggs and the caterpillars, and scores of other creatures which consider them fair prey. Camouflage is often practiced in a pe culiar way. For example, our colorful friend, the Viceroy (see Color Plate II, figure 7), copies the Monarch (see Color Plate IX, figure 12) to perfection. Now, the Monarch happens to be a very dis tasteful creature to a bird because of its acrid blood; but a Viceroy makes a de lightful titbit. The bird, because of wider experience with the Monarch, usu ally lets the similarly colored Viceroy severely alone. This theory was tested on a monkey, who was given a Monarch to eat; he threw it aside in disgust. Next he was given a Viceroy, and as promptly he cast it aside. Then another Viceroy was of fered, this time with the wings pulled off. It was eaten with evident relish. Many other bird-relished species follow the practice of the Viceroy and imitate acrid varieties, thereby obtaining protec tion. GAY COLORS DAZZLE THE PURSUER Even the gay colorings of our gaudiest butterflies and moths are now thought by leading authorities to be protective, those who hold to this belief asserting that a woodpecker often loses a meal because disappearing brilliancy causes him to lose track of his quarry. As he chases a showy butterfly, his eye is full of the bright color, but when the insect alights it folds its wings above its back and, presto, the bright color disappears! Instead, it shows the drab hue of the underwing, harmo nizing with its surroundings. With the folding of its wings the insect becomes a part of its background and the thwarted woodpecker flies away, doubt less wondering how that bit of bright color escaped his hungry eye. One of the Orange Sulphurs of the Pikes Peak mead ows, related to those shown on Color Plate IV, is green underneath. A brilliant flash of color while flying, it seems to vanish when it alights in the grass and closes its wings. In the Kallima, or Dead-leaf Butterfly, this scheme is strikingly carried out. The underwing surface bears a remarkable re semblance to a leaf. It even has a hind wing projection which looks like the stem of a leaf, and a mark running across the wing appears to be a midrib. Perched on a twig, with closed wings, it perfectly simulates a dead leaf, but with outspread wings it is brilliant bait for a bird (see illustration, page 120). In the case of the moths, which rest with folded wings instead of upright ones, as do the butterflies (see illustrations, page 85, and Color Plate XV), the brilliant color is on the rear wing, which is covered up by the somber forewing when the in sect is at rest. Studies of grasshoppers, locusts, and other winged insects show how this idea of disappearing brilliant colors runs through many families of the entire winged clan. In collecting moths, one discovers that those which live among the birches usu ally have a coloration approximating the tones of birch bark, while those which are found usually on the trunks of maple trees show color schemes that make their visibility low. Figures I and 2 on Color Plate XII show the contrast between the two species, which are closely related. But the beelike moths carry the art of camouflage even further than mere pas sive color protection. If captured or dis turbed, they act exactly like the bees they simulate, give off the familiar bee odor, and even pretend to sting, in spite of the fact that they have no stinging apparatus. MAKING MONSTERS OF THEMSELVES TO WIN PROTECTION The caterpillars employ many of the arts of camouflage used by the adult but terflies and moths. The measuring-worms, larvae of the Geometrid moths, simulate in color and general appearance the twigs on which they rest. Disturbed, they stand on their hind legs and look for all the world like small projecting shoots.